Robots have been widely used for many years in the field of industrial manufacturing where, thanks to their ability to reproduce pre-programmed sequences of operations within a short time, an infinite number of times, they make possible significant rationalizations in production. Since such robots are in most cases also designed to relieve humans of fatiguing working steps like handling heavy workpieces, they are correspondingly robust in construction and at most can only be deflected slightly through an external impact. Conversely, due to their considerable mass and rapid movements, these robots are quite capable of injuring personnel working in their vicinity. In order to avoid a collision with persons, industrial robots are therefore generally surrounded by a cage when in use.
Robots which are designed for use in the operating theatre cannot, for practical reasons, be shielded by means of a cage, since in general they do not perform an operation on their own; medical personnel are also working on the same patient at the same time. A collision between such a robot and the personnel cannot therefore be prevented with absolute certainty. Since a surgical robot is generally lighter and slimmer in construction than a production robot, in order to avoid unnecessarily blocking the personnel's view of a surgical field, in the event of a collision a deflection of the robotic arm cannot be wholly prevented. If a tool being handled by the robotic arm is also thereby deflected, this could injure the patient.
It is possible to equip a robotic system with appropriate sensors for detecting any impending collision and with a control unit which, when a collision is predicted, controls an evasive movement of the robotic arm in order to avert the impending collision. However, the possibilities for such an evasive movement are limited when the robotic arm is handling a tool on or in the patient's body which may not be moved at will.
It would be ideal if, in such a situation, only a central section of the robotic arm which connects the base with the tool could perform an evasive movement, while the tool itself remained in position. However, the number of degrees of freedom of the robotic arm is generally only as large as is necessary in order to perform the desired movements of the tool. Therefore, there is a not insignificant likelihood that the degrees of freedom of the robotic arm are not sufficient for an evasive movement in which the tool remains immovable. In such a case, an evasive movement can at best be performed in which the resulting movement of the tool is safe for the patient.
If the tool is a camera, in particular an endoscope camera, the problem arises that any movement of the camera changes the image which it provides of its surroundings. Any movement of the camera can therefore lead to a user who is observing the images supplied by the camera on a screen losing sight of an object which is of interest to him. This possibility exists both with a movement of the camera controlled by the user himself as well as when it moves due to the robotic arm being jolted or in connection with an evasive movement of the robotic arm. In the latter two cases the likelihood is, however, particularly high.
Known from WO 2012/078989 A1 is a robotic system with a movable camera on a robotic arm which can be introduced into the body of a patient through a trocar sleeve in order to monitor a tool. A control unit calculates, on the basis of a known aperture angle of the field of view of the camera and known positions of camera and tool, whether the tool lies in the field of view of the camera. If this is not the case, then the camera is moved away from the tool in order to bring the tool into the field of view. If the tool is to be shown larger, the camera is moved towards the tool, insofar as this is possible without losing the tool from the field of view. The monitoring of other objects, in particular of tissue parts of a patient, is not facilitated with this robotic system.
There is therefore a need for a robotic system with a camera in which the likelihood that an observed object is lost from sight through a movement of the camera is reduced.